1. Field of the Invention
The present invention generally relates to pumps, and more particularly to positive-displacement rotary pumps.
2. Description of the Related Art
Positive displacement pumps displace a known quantity of liquid with each revolution of the pumping elements (e.g., vanes). Positive displacement pumps displace liquid or gas by creating a space between the pumping elements and trapping the liquid or gas within the space. Rotation of the pumping elements then reduces the volume of the space and moves the liquid out of the pump. A rotary vane pump is an example of a positive-displacement pump.
Rotary vane pumps operate through the action of a number of rotating vanes or blades. A conventional rotary vane pump includes a rotor assembly eccentrically positioned within a pumping chamber. The number of vanes are spaced around the rotor to divide the pumping chamber into a series of cavities. As the rotor rotates, these cavities rotate around the pumping chamber continually changing in volume due to movement of the vanes and the eccentric alignment of the rotor and pumping chamber. An inlet communicates with the pumping chamber on the side of the pump where the volume of the cavities expand. Similarly, an outlet communicates with the pumping chamber on the side of the pump where the volume of the cavities contract. As each cavity expands, a partial vacuum is created to draw fluid into the pump through the inlet. As the cavity contracts, the pressure within the cavity increases forcing the fluid out of the pump through the outlet. This expansion and contraction process continues for each cavity to provide a continuous pumping action.
There is a desire to improve upon the currently available rotary pumps. For example, there is a desire to reduce the cost of manufacturing rotary pumps while maintaining (and possible increasing) the vacuum level produced by a pump of specific dimensions. There is also the desire to increase the volume of fluid that can be displaced during a period of time by a pump of specific dimensions (i.e., without increasing the overall dimensions of the pump). Further, there is the desire to simplify the manufacturing and assembly required for producing rotary pumps.